The bladder is an organ that collects urine excreted by kidneys before disposal by urination. As urine accumulates in the bladder of a patient, increases the bladder volume of the patient and thus increases the internal pressure of the bladder. In response to the increased internal pressure of the bladder reaching a critical pressure level, the patient may feel the urge to urinate.
There are several conditions which may affect urination from the bladder of a patient. Bladder dysfunction, e.g., incontinence and urine retention, is one of them. Another condition is marrow nerve damage due to which a patient cannot respond to internal pressure of his/her bladder. Generally, such marrow nerve damage may be caused by trauma.
Several methods have been used for patients suffering from such conditions. One method is to implant a pressure sensor into the bladder of the patient and detect the moment at which the pressure of the bladder, indicated by the pressure sensor, reaches a critical pressure level. However, implantation of a pressure sensor is invasive and often very expensive. Another method is to measure the bladder volume of the patient non-invasively using ultrasound imaging. Several devices for automated portable bladder volume measurement have been developed based on ultrasound imaging techniques. However, the devices are designed for general checking in daily clinical practice and their battery can be used for several hours only, therefore, the devices are not suitable for long-time monitoring and warning.
U.S. Pat. No. 6,372,951 B1 discloses a disposable article to be fitted to a wearer. The disposable article preferably comprises a sensor operatively connected to the article. The article may comprise a monitoring system including a piezoelectric transducer that measures the volume of a fluid-filled cavity in the body, such as a bladder or rectum. When stimulated, the piezoelectric transducer sends an ultrasound pulse into the abdomen. The pulse may be sent out at any pre-defined or random interval.